1. MJO Modulation of Lightning in Mesoscale Convective Systems
Katrina S. Virts and Robert A. Houze, Jr.
University of Washington
AGU Fall Meeting, San Francisco, 11 December 2013

2. Identifying MCSs using A-Train data
MODIS 10.8 m brightness temperature
AMSR-E rain rate
Years included:
MODIS = moderate resolution imaging spectroradiometer; AMSR-E = advanced microwave scanning radiometer for earth observing system
Details in Yuan and Houze 2010

3. “Separated” active MCS
260K
Heavy Rain
Closed contour
Rain
“Separated” active MCS
Separated
HCS
“HCS”
Avg CMCS = km2; SMCS = km2
“Connected” active MCS
Details in Yuan and Houze 2010

4. World-Wide Lightning Location Network (WWLLN)
Global network of 70+ sensors
Monitors very low frequency radio waves
Lightning strokes located to within 5 km and a few s

5. World-Wide Lightning Location Network (WWLLN)
Global network of 70+ sensors
Monitors very low frequency radio waves
Lightning strokes located to within 5 km and a few s
Lightning in one-hour window
Separate coordinate system for each MCS, centered on largest raining core
Lightning in cloudy grid boxes

6. MCS climatology Indian Ocean Maritime Continent Western Pacific Ocean
SPCZ

7. More frequent lightning, broader lightning maximum during break period
Maritime Continent SMCSs
Active period - phases 3-4-5
Break period - phases 7-8-1
60% increase in ltg freq during break period; 40% increase in MCS size during active period
More frequent lightning, broader lightning maximum during break period

8. MCS environments more unstable during break period

9. Peak lightning at end of break period Lower lightning density in CMCSs

10. TRMM radar precipitation features
Contiguous areas with near-surface rain rate > 0
Use features with maximum height of 30 dBZ > 6 km
Size equivalent to smallest and largest 50% of MCSs
Years included:
TRMM RPF data obtained from University of Utah TRMM database. Details in Liu et al. 2008

11. Peak convective rain fraction at end of break period
Lower convective rain fraction in large precipitation features

12. Conclusions
Larger, more connected, and more numerous MCSs during MJO active period
Peak lightning just prior to active period (except over SPCZ)
Lower lightning densities and lower convective rain fractions during active period
Higher lightning densities in SMCSs

13. The End
This research was supported by NASA grant NNX10AM28G and DOE grant DE-SC